1. Field of the Invention
The present invention relates to a photoresist stripper composition containing the combination of (1) selected solvents; (2) selected amines; (3) selected chelating reagents; and optionally (4) selected corrosion inhibitors.
2. Description of the Prior Art
The photoresist stripper art is replete with numerous references to stripper combinations containing both a polar solvent and an amine compound. The presence of an amine in photoresist stripper compositions has been judged to be essential to effectively remove cross-linked resist films. However, amine-type photoresist strippers sometimes have a serious problem of corrosion, especially with aluminum substrates.
It is believed that the corrosion is caused in part by the ionization of water with the amine in post-stripping water rinses, as residual stripper solution may be retained on the substrate surface and/or substrate carrier after the stripping step. In other words, the amine component of the stripper composition does not corrode the substrate by itself, but may trigger water to cause the corrosion.
To solve this problem, an intermediate rinse step with an organic solvent has been used between the stripping step and the post-stripping rinse with water. For example, isopropyl alcohol is known to be useful for this purpose. However, such intermediate rinses are not necessarily desirable because overall stripping operation becomes more complicated and, furthermore, an additional solvent waste is produced. Accordingly, if amine-type strippers are to be further employed, there is a need to solve this corrosion problem without intermediate organic solvent washes.
Another serious problem related with currently used stripper compositions is mobile metallic ion transfer from a stripper solution onto a substrate. This results in damage of semiconductor integrated circuit devices by contamination with alkali or transition metals. Any metallic contamination leads to a short life of the devices.
The metallic contaminants may come from stripper components or photoresist components. Another mechanism of the contamination is corrosion of a stainless stripper bath with a stripper composition, particularly with an amine-based stripper, during the stripping process.
To solve this problem, several actions have been taken:
(1) Removal of metallic contaminants from strippers and photoresists as much as possible.
(2) Inhibition of the corrosion of stripper bath by adding a corrosion inhibitor to stripper compositions.
(3) Stabilization of mobile metallic ions in a stripper solution by adding a chelating reagent to stripper compositions.
Illustrative of references suggesting photoresist stripper compositions containing the combination of a polar solvent and an amine compound are the following:
1. U.S. Pat. No. 4,617,251, which issued to Sizensky et al. on Oct. 14, 1986, teaches a positive photoresist stripping composition containing (A) selected amine compound (e.g., 2-(2-aminoethoxy)ethanol; 2-(2-aminoethylamino)ethanol; and mixtures thereof) and (B) selected polar solvents (e.g., N-methyl-2-pyrolidinone, tetrahydrofurfuryl alcohol, isophorone, dimethyl sulfoxide, dimethyl adipate, dimethyl glutarate, sulfolane, gamma-butyrolactone, N,N-dimethylacetamide and mixtures thereof). The reference further teaches that water as well as dyes or colorants, wetting agents, surfactants and antifoamers may be added into this composition.
2. U.S. Pat. No. 4,770,713, which issued to Ward (J. T. Baker) on Sep. 13, 1988, teaches a positive photoresist stripping composition containing (A) a selected amide (e.g., N,N-dimethyl acetamide; N-methyl acetamide; N,N-diethyl acetamide; N,N-dipropyl acetamide; N,N-dimethyl propionamide; N, N-diethyl butyramide and N-methyl-N-ethyl propionamide) and (B) selected amine compound (e.g., monoethanolamine, monopropanolamine, methyl-aminoethanol). The patent also teaches this stripper may optionally contain a water miscible nonionic detergent (e.g., alkylene oxide condensates, amides and semi-polar nonionics).
3. U.S. Pat. No. 4,786,578, which issued to Neisius et al. (Merck) on Nov. 22, 1988, teaches a rinse solution used after a photoresist stripper, said rinse solution containing (A) a nonionic surfactant (e.g., ethoxylated alkylphenol, fatty and ethoxylate, fatty alcohol ethoxylate or ethylene oxide/propylene oxide condensate) and (B) an organic base (e.g., mono-, di-, or tri-ethanolamine).
4. U.S. Pat. No. 4,824,762, which issued to Kobayashi et al. (TOK) on Apr. 25, 1989, teaches photoresist stripping post-rinse solution containing (A) glycol ether (e.g., diethylene glycol monomethyl ether, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether) and (B) an aliphatic amine (e.g., monoethanolamine or tri-isopropylamine).
5. U.S. Pat. No. 4,824,763, which issued to Lee (EKC) on Apr. 25, 1989, teaches positive-working photo-resist stripping composition containing (A) triamine (e.g., diethylene-triamine) and (B) a polar solvent (e.g., N-methyl-2-pyrrolidone, dimethylformamide, butyrolactone, aliphatic hydrocarbons, aromatic hydrocarbons, chlorinated hydrocarbons).
6. U.S. Pat. No. 4,904,571, which issued to Miyashita et al. on Feb. 27, 1990, teaches printed circuit board photoresist stripper composition containing (A) a solvent (e.g., water, alcohols, ethers, ketones, chlorinated hydrocarbons and aromatic hydrocarbons); (B) an alkaline compound dissolved in said solvent (e.g., primary amines, secondary amines, tertiary amines, cyclic amines, polyamines, quaternary ammonium amines, sulfonium hydroxides, alkali hydroxides, alkali carbonates, alkali phosphates and alkali pyrophosphates); and (C) a borohydride compound dissolved in said solvent (e.g., sodium borohydride, lithium borohydride, dimethyl amine borone, trimethyl amine borone, pyridane borone, tert-butyl amine borone, triethyl amine borone, and morpholine borone).
7. U.S. Pat. No. 5,279,791, which issued to Lee on Jan. 18, 1994, teaches a stripping composition for removing resists from substrates containing (A) hydroxylamine (e.g., NH.sub.2 OH); (B) at least one alkanolamine; and optionally (C) at least one polar solvent.
8. U.S. Pat. No. 5,334,332, which issued to Lee (EKC) on Aug. 2, 1994, teaches the use of ethylenediamine tetraacetic acid and 1,2-dihydroxybenzene as a chelating reagent to reduce the surface metal contamination on wafers.
9. German Published Patent Application No. 3828513, which published on Mar. 1, 1990 and is assigned to Merck GMBH, teaches a positive and negative photoresist stripper composition containing (A) an aprotic polar solvent (e.g., 1,3-dimethyl-2-imidazolidinone or 1,3-dimethyl-tetrahydro-pyrimidinone); and (B) an organic base (e.g., alkanolamine).
10. Japanese Published Patent Application No. 56-115368, which was published on Sep. 10, 1981 and is assigned to San Ei Chemical Industries, KK, teaches a photoresist stripping composition containing (A) nonionic surface activator (e.g., a polyethylene glycol ether); (B) organic solvent (e.g., cyclohexanone); and (C) either a swelling agent (e.g., polyethylene glycol) or penetrant (e.g., 2-aminoethanol).
11. Japanese Published Patent Application No. 63-208043, published on Aug. 29, 1988, teaches a positive-working photoresist stripper composition containing (A) 1,3-dimethyl-2-imidazolidinone; (B) a water-soluble organic amine (e.g., monoethanolamine, 2-(2-aminoethoxy)ethanol, triethylene(tetramine). The application also teaches a surfactant may be added to the stripper.
12. Japanese Published Patent Application No. 1-081949, which published on Mar. 28, 1989 and is assigned to Asahi Chemical, teaches a positive-working photoresist stripper composition containing (A) gamma-butyrolactone, N-methyl-formamide, N,N-dimethylformamide, N,N-dimethylacetoamide or N-methylpyrrolidone; (B) an amino alcohol (e.g., N-butyl-ethanolamine and N-ethyldiethanolamine); and (C) water.
13. Japanese Published Patent Application No. 4-350660, which is assigned to Texas Instruments, Japan and Kanto Chemical, Inc., teaches a stripper for positive photoresists comprising (A) 1,3-dimethyl-2-imidazolidinone (DMI), (B) dimethylsulfoxide (DMSO) and (C) a water-soluble amine (e.g., monoethanolamine or 2-(2-aminoethoxy)ethanol wherein the amount of the water-soluble amine is 7-30% by weight.
14. Japanese Published Patent Application No. 5-045894, which published to Ward (ACT, Inc.) on Feb. 26, 1993, teaches the use of 6-hydroxyquinoline as a chelating corrosion inhibitor in a positive photoresist stripper.
In particular, recently, the approach with chelating reagents to reduce the surface metal contamination has attracted much attention. However, most of the compounds so far used have several problems like a poor solubility in a stripper solution, a strong acid/base reaction with a stripper component, or a higher toxicity.